Protective device



April 24, 1928. 1,666,923

W. W. WOODRUFF l PROTECTIVE DEVICE Filed NOV. 5 1922 3 [I I0 9 Il ":mllglluw y vwentoz rm ull Patented Apr. 24, 1928.

UNITED STATES PATENT OFFICE.

PROTECTIVE DEVICE.

Application 'filed November My invention has to do with a small unit or accessory which is particularly adapted to protect large or expensive pieces of apparatus from being destroyed by reason of the existence of abnormal operating conditions. rThe unit may be considered yas a vcut. out, that is, an article Which operates to prevent further operation of all or a part of a selected apparatus or a system.

The unit may be employed for many different purposes and in conjunction with.

many different types of apparatus, but I have found -that it has a particularly successful use when employed With transformers mounted in electrical power transmission lines. The description of the unit and its use will therefore be ,made in connection with this particular type of apparatus, although l desire that it be understood that the unit may be employed with other apparatus and particularly With other electrical apparatus.

lt Well known in lthe 'transmission of electrical power from the generatingr station to 'the consumer, that the greatest efficiency is obtained by the use of transformers installed selected points. Usually these transformers are located in isolated places Where persons seldom pass so that the danger of accident from the high voltages is reduced to a minimum. Or when the trans rormers are employed at factories, they e re so located and protected so that persons without authority are unable to come within the Zone of danger, consequently the working conditions of the transformers are ob'- served but seldom.

Since it has been found in practice that the best method of rating a transformer as to its continuous l. v. a. capacity is by determining the maximum temperature at which vitis safe to operate the internal insulation at constant load, it has heretofore been necessary to periodically observe the temperatures of the parts of 'the transformers in order to operate them at their best eliiciency.. lVhen the transformers are erected inv the power house the temperatures may be readily observed by an operator but he moet necessarily come Within close prox 3, 1922. Serial No. 598,733.

imity with th-edangerous high tension Wires. When the transformers are located away from the power house, the user has elected to eliminate the cost of men, for inspection, by increasing his installation costs by purchasing transformers of larger capacity which operate at a much lower efficiency. lt therefore becomes desirable to eliminate this extra initial cost and to operate the transformers at their best eliciency While at the same time protecting them from destruction When operatedA at dangerous temperatures. f

The best present practice in the construction oftransformers is rto immerse the core and the windings in an oil bath and to provide as large a cooling surface as possible for the oi-l. However, the rating of a transformer is still based upon 'the maximum temperature for the continuous k. v. a. capacity.

By reason of the nature of the load curve on most transmission systems, the transformers are loaded to rated capacity lfor only a very small portion of the time, and When it is considered rthat each transformer has a large rthermal capacity, Which requires about ten lhours to reach maximum temperature under rated load, it is seen that the temperature remains much below its permissible value ythereby decreasing .thevefiiciency of the transformer to a very low point.

It has been the practicein the recent past to operate transformers at higher ratings and temperatures in order to take advantage of the installed k. v. a. capacity of a 'trans mission system. The present rating of a transformer is of little value, as the determining faetor is the 'temperature attained during the .load cycle. Already several different types of temperature indicating `devices have been developed, but each one requires that an attendant be employed to record the temperatures, and none of vthese devices operate to protect the transformer' from being burned out which necessitates 'the expense of dismantling and the rewindin of the coils.

i y invention therefore consists, lin general, of an accessoryv which readily ina corporated in an aljnjlaratus so that it will operate under predeeriniiiied conditions to protect the apparatus from injury. More in particular, my invention consists of a novel association and operation oi elements forining an accessory lfor electrical apparatus so that when assembled therewith it will be influenced by the operating conditions of such apparatus to cutottA the power and thereby prevent destruction ot the apparatus.

As has been heretofore stated, my device is especially adapted tor use in transformers and l have therefore constructed it in a novel fashion which permits it to be affected by the temperature of the cooling medium such as oil flowing in a transformer and is so arranged as to have this cooling inediun'i operate as an extinguisher 'tor the arcs created when the power circuit. to the electrical portions ot the transformer .is opened.

A proper conception ot my invention may be readily obtained by considering its operation in connection with one ol? its successful uses, that is, on a transformer. Usually a unit is mounted in series with each lead-in conductor oit the transformer and is immersed in the circulating oil. The unit carries separable contacts and is provided with a temperature responsive alloy to hold the contacts in current conducting relation. The oil is permitted to flow in and around the contacts and the alloy. `When the teinperature ol the oil has reached a value, by reason of the operation of the trans- Jformer, which makes it dangerous to tun ther operate the transformer, the alloy is fused and the contacts are allowed to automatically separate thus interrupting the flow of current. This oil, which is the circulating` medium performs another function be sides melting the alloy. lt acts to extinguish the arc Vtermed between the contacts as they separate thereby preventing injury to the unit or to the transformer itselt.

lt will therefore be seen that the use ot my accessory will permit the transformers located in isolated spots and especially those transformers which are not subject to a regular inspection, to be operated at maximum eiliciency without danger of being destroyed.

In describing my device .in detail reference may be had to the accompanying drawing wherein a selected embodiment of the invention is illust-rated, and in this drawing Fig. l is a sectional View of the device showing the several parts in normal operating relation;

Fig. 2 is a sectional view of part of my device showing a modified construction for holding two contacts together for normal operation; and

Fig. 3 is a perspective view of a plug adapted to be employed in the construction shown in Fig. 2.

tiefer-ring now to this drawiiiig, the accessory or unit preferably consists ot an insulating casing l provided with a stationary Contact 9. and a suitable movable contact 3, a current conducting plug e, affixed in one end ot the casing, a spring 5 to move contact 3, and a flexible current con ducting cable 6 connecting the contact 3 and the plug il. The contacts 2 and 3 are held in normal current conducting relation by a suitable alloy 7 which is preferably in solder torni or is soldered in position. This particular cone struction ot my device illustrates one manner in which the alloy is ei'i'iployed so that it may be melted to permit the contacts to separate thereby opening the energy circuit.

l have found that the construction illustrated in Fig. l is avery high etiiciency troni both the manufacturing and the operating standpoints. The casing l. is preferably cy` lindrieal and is easily tabricated from the ordinary fibre or other insulating tubing. The contact 2 and the plug l are readily assembled in the opposite ends olI the casing and may be held in position by suitable means such as suitable screws. For purposes of obtaining a large contacting surface between the contacts 2 and 3, l have bored out contact 2 so that it will receive the contact 3 in a telescoping manner. reiierably contact 3 is 'termed ot metal tubing so that the circulating medium may have `substantially equal etlect on all ol' the alloy. The casing l and the contact 3 are provided with openings 9 and lO respectively to permit the tree circulation of the oil and it is to be understood that these openings may be Ytermed at different points so as to obtain desired resuits for di'tlerent conditions ot operation.

The spring and Flexible conductor means 'for joining the Contact Zl and the plug /ll to produce the nii-'lans for separating the contacts and for maintaining :l current conoci:- tion to contact Sl, have been very successful in operatioin but when desired other constructions inay be employed to perform these functions. For purposes ot properly poso tiornng and guiding Contact 9) when it is withdrawn Yfrom coi'itact l, have provided suitable rings ll which en the interior ot' the casing and which are held in position by suitable screws 8.

'lhe constluiction, ol' iny device permits it to be readily installed in each oi' the transl'oriner leadein conductors Yand. to be positioned below the surface ot the main body ot the circulating oil. it is to be understood however', that the devices may be located elsewhere and have the oil squirted over them in such a manner that the alloy will be properly affected and preferably so that the quantity of oil will be sutiicient to assist l in extinguishing the arcs formed as the contacts separate.

is is well known in the operation oi translill? formers, the "oil. surrounds the core/and the created and thenA rises. in temperature. The volume of the oil is large and vtherefore some of it has an portunity 'to cool white other portions are a'sorbing heat from ithe transyformer parts, but in time the Whole body yot' t'lre oil becomes heated and is 'then not able to conduct the heat away from the core and Win-dings.. At this point it is dangerousto further operater the transformer and my dvice then functions to open the circuit. The alloy employed in my device may be 'any combination Iot' materials desired so long as itis responsive to the thermal condition of the oil. 1t is usually arranged so that it is responsive at a temperature slightly below the` maximum temperature at` which it is conducting relation.

ranged so-that all Iof the force required vto keep 1contact '3 yin 'engagement withwzoutact 2 against the force. of' spring 5 will not be offered by the plug. Such an allocation of the resisting forces is of value in the devices constructed'to transmit large amounts 'of power.

InVFig, 2 I have illustrated fone way of maintainin g the plug in. the ldevice but other means may "be employed. My preferred method'is to provide. the plug Wii'th a head 14 which Aclrgages a rgroove 15 formed in the casing. thus I have provided against Athe 'slippingof the plug from the casing. An ear 16 adapted to engznge notch 17 preventsthe plug from turning so that lug 13 will always be` in ycontact with ring 11 until it is melted permitting the Contact i3ft-o be ldrawn away from AContact Q.'

l-t will be seen from the lfor'egoing description that 1 have provided la 'novel and simple means for protecting large and expensive apparatus, and I'ihave so arranged my device that it is responsive to 'the condition 'of operation of the 'device but is not responsive 'to temporary overloads in the-energy circuit. il, however, Wish to be understood that my device is particularly responsive to the operating conditions of the elements of the apparatus and notl to the amount of energy which passes through them. Ordinarily cut` outs or fuses of this nature in electrical `apparatus a-re responsive to the amount of` power passing throng-h the ypower lines and Athey give way to open the circuit by reason ofthe-existence of an abnormal amournt'of power. In constructing my device so that it is responsive to the conditions ofthe operating elements ofthe apparatus, l provide the alloy iny such amounts that the existence ot' abnormal amounts of power passing through the valloy has no 'effect in so tar as 'releasing 'the device to open the circuit' is concerned by heating the alloy or otherwise. My device is pe'r'ff'eoted to open the current lines when the apparatus continues to operate under conditions which are detrimental to the elements iof the apparatus. It will be understood that While 1 have :shown my device as being connected in series in the line of a transformer. I may connect my device in a circuit which will control :a circuitbreaker `or any `other desired form of means 'for releasing the transformer nor other apparatus-from its operation in the circuit.

Various changes and lmodifications maybe made in the construction illustrated, but such variations are considered @as being Withinthe scope ot' my invention sis-outlined in the yswbjoined claims.

I claim:

1. In ka protective device constructed to operate when .predetermined operating'conditions have been reached, the :combination 'of a casing perforated lto :allow .a Huid :to pass in engagement with the inside andeutside thereof, a pair of elements vsupported by Vsaid casing so as to :be norma-lily held .in loperative rei ation to one another and adaptedy to be moved apart under predetermined operating conditions, .said elements boing mounted to have saii'd'iuid pass in contact therewith, fmeans for holding aid felenlients in normal operative relation, 4said means be ing responsive vto va predetermined condition Aott' said 'luid, and means rtor positively moving said elements out of' normal operative relation 'when the predetermined operating conditions have been reached.

In a protective device constructed to operate when predetermined operating conditions have been reached, the Icombination of'a casing perforated to :rlilow a fluid to passthereth-rougih, a pair oi elements supported within said casing and being so frnounted as to be normally heldin operative relation to one another and adapted to be moved apart under predetermined oi'ieratiug yconditions, the lpert'orations in said casing permitting the Huid to pass in Contact wi th said elements, means for holding said elcments in normafl operative relation and bcing responsive to 'the temperature condition of said iuid, said holding lmeans being suhjected Ato strains dulri'ng said holdingoperation, and a resilient means afiixed to one of' said elements for moving said elerrient out of operative relation with the other element after said holfdingfrneans fhas been acted upon by said fluid to cause said holding means to release said elements, said resilient means being mounted Within said casing.

ln a protective device constructed to operate when predetermined operating conditions have been reached, the combination of a casing perforated to alloiv the fluid to pass therethrough, a pair of electrical contacts mounted within said casing, an electrically conducting material associated with said contacts for holding the same in operative relation to one another to thereby permit electricity to be conducted through said device, and means associated With one of said contacts for continuously tending to move said contact out of its operative relation with the other contact, said contacts being supported in said casing so that 'heat absorbing medium may engage said cont-acts when :aid device is positioned to have said heat absorbing mediun'i brought into relation therewith.

4l. An electrical device for protecting a large electrical apparatus, said device consisting of a casing, a stationary electrical contact therein forming one terminal of an electrical circuit which controls the operation of the apparatus, movable Contact for engagement with said stationary contact, said movable Contact forming the other ter minal of the control circuit, means associated Wit-h said movable contact and acting to move said contact from said stationary contact when said contacts are released, and a fusible material for holding said contacts together, said material adapted to conduct the current in said circuit from one terminal to the other Without becoming heated by the passage of current therethrough, said device being placed in juxtaposition to said apparatus to have said fusible .material res ponsive to the heat developed by said ap- `paratus and by the separation of said coutacts to release said apparatus from opera tion due to the existence of abnormal teinperature of said apparatus.

5. temperature limiting device for use `with transformers consisting` of a perforated caring. a stationary and a movable contact therein, a spring mea-ns tending to maintain the movable contact away from the station-I a y' contact, and an alloy forming a part of said device and adapted to hold said conlacts in current conducting relation, said casing arranged to admit the oil from the transformer into Contact with said alloy to melt the saine and interrupt the flow of current When the oil has reached a predetermined temperature.

6. A protecting device for use with electrical apparatus consisting of a perforated casing,apair of contacts carried by said casing and being so arranged as to be automatically separated at a predetermined temperai-,eeaeas tioned Within said casing in a manner to hold said contacts in normal. operating relation, said casing adapt-ed to be held in a circulating medium which acts upon said alloy to melt it and allow said cont-acts to separate, said medium acting to extinguish an are formed by the separating of said con facts.

7. A protective device for use in transformers consisting of a perforated insulating tubing, electrical conducting pieces affixed Within said tubing at the ends thereof, a metal tubing adapted to telescopically engage one of said pieces, a flexible electrical conductor engaging the other of said pieces and said tubing, a spring also engaging said last named piece and said metal tubing and tending to draiv said metal tubing from said first named piece, and a fusible alloy adapted to hold said lirst named piece and said metal tube together to permit the passage of current, said device adapted to be immersed in the oil of the transformer so that the oil may fuse the alloy andfallow the contacts to draw apart, said oil further acting to quench the arc formed by the separation of the conducting parts.

8. A device for opening the electrical current of a transformer under predetermined condition of operation of said transformer consist-ing` of a perforated insulating tubing, a stationary contact allixed Within one end of said tubing, a perforated movable contact adapted to telescope into said stationary contact, a. current conduct-ing` plug athxed in the other end of said tubing, a spring engaging said movable Contact and said plug tending to Withdraw said movable contact from said stationary contact, a flexible current conductor joining said movable contact and said plug and being' located Within said spring, and a fusible alloy for holding the teleseoping contacts in current conducting relation, said device adapted to be immersed in the oil of the transformer so that the oil passes through the perforations and into contact with the fusible alloy and said contacts, said alloy arranged to be melted by the oil at a predetermined temperature thereby allowing said contacts to separate and said device being so constructed that the oil acts to extinguish an arc formed by the separating of said contacts.

9. ln a device of the character described the combination or relatively movable ele ments adapted to be held in normal operating position, and a thermal responsive member for maintaining said elements in operative relation, said device adapted to be immersed in a medium of greater density than air which acts upon said thermal responsive member and which operates to prevent injury to device when .said relatively movable elements are moved out of normal operating position.

10. In a device of the character described, the combination of relatively movable contarots normally held in current Conducting relation against the opposition of a resilient member, a thermal responsive alloy interposed between said contacts Jfor holding them in normal position, the amount of said alloy being suioient to conduct excessive Currents due to abnormal disturbances Without becoming sufficiently heated to release said contacts, said device being subjected to a heat absorbing medium which operates to melt said alloy to permit the separation ot said Contacts and operates to extinguish dangerous arcs formed by the separating ot said Contacts.

In testimony whereof, 'I have signed my name to this specification this 19th da)7 ot October 1922.

WV. VARREN WOODRUFF. 

